Graded pressure drop type detection system and detection method of borehole cracks

ABSTRACT

Within the technical field of detecting a mining-induced failure range of rock mass, and particularly relating to a graded-pressure drop type detection system and detection method of borehole cracks, a detection system is provided including a test probe, a drilling rig, a drill pipe and a control operation platform. The test probe includes a plugging device and a pressure conversion assembly. The pressure conversion assembly is connected with the plugging device at the rear end through a connected pipe and includes a first stage pressure converting device and a second stage pressure converting device. The detection system simplifies the existing operating system, avoids the problem of drill pipes winding in drill hole, realizes plugging process and detection process with the same external water source, and ensures that the plugging process and the observation process operate under respective predetermined pressures.

TECHNICAL FIELD

The present invention belongs to the technical field of detecting a mining-induced failure range of rock mass, and particularly relates to a graded pressure drop type detection system and detection method of borehole cracks.

BACKGROUND

The measurement of floor mining failure height (or depth) in mine is an important parameter to indicate the occurrence state of coal and rock. It is a key basic parameter in the research of mine water prevention and control. Therefore, it is necessary to grasp the strata movement law and determine the height determination of the mining failure zone in order to investigate the formation of water inrush channel in mining surrounding rock. Series of detection equipment represented by “device for measuring leakage with double ends plugging of borehole” for in-situ testing, have the problems of tedious operation process and drill pipe winding because the plugging operation table and the water supply operation table are independent and correspondingly connected with more than two pipelines and test probes in drill hole, thus resulting in poor stability and low effectiveness during observation. In series of products, although the problem of single loop can be solved, there are problems of large conversion range of water pressure, poor conversion stability, difficult control of water pressure and easy mechanical failure. The prior art fails to simultaneously solve the above problems.

SUMMARY

The purpose of the present invention is to provide a graded pressure drop type detection system and detection method of borehole cracks.

The technical solution of the present invention is:

A graded pressure drop type detection system of borehole cracks comprises a test probe, a drilling rig 14, a drill pipe 12 and a control operation platform 36, wherein

the test probe comprises a plugging device and a pressure conversion assembly 47; the plugging device comprises a plugging device at the front 34 and a plugging device at the rear end 35; the pressure conversion assembly 47 is connected with the plugging device at the rear end 35 through a connected pipe 28 and comprises a first stage pressure converting device 6 and a second stage pressure converting device 37; the second stage pressure converting device 37 is sheathed on the outer end of the first stage pressure converting device 6 and is in threaded connection with the first stage pressure converting device 6.

The plugging device comprises a water leakage pipe 3, a joint and a rubber bag 5; the rubber bag 5 is wrapped around the outer end of the water leakage pipe 3, and forms a blocked cavity 30 with the water leakage pipe 3; both ends of the rubber bag are fixed by a fastening iron ring 24; a water leakage hole 25 is formed in the water leakage pipe 3; an outside water source enters the blocked cavity 30 through the water leakage hole 25 in the water leakage pipe 3; a water injection cavity 29 is formed between the swelling rubber bags 5 and drill hole 31.

The drilling rig 14 is connected with the test probe through the drill pipe 12 for extending and pushing the test probe to a designated region; the drill pipe 12 is a hollow pipe in which the outside high pressure water source can be delivered; the drill pipe 12 and the test probe are in threaded connection and are detachable.

The control operation platform 36 is connected with the drill pipe 12 through a high pressure resistant hose 13 and is responsible for providing the outside water source with designated pressure for the test probe and displaying parameters such as pressure and flow.

The plugging device at the front 34 consists of a type I joint 2, a water leakage pipe 3, a type II joint 4 and a rubber bag 5; the type I joint 2, the type II joint 4 and the water leakage pipe 3 are in threaded connection; the rubber bag 5 is wrapped outside the water leakage pipe 3, is fixed outside the type I joint 2 and the type II joint 4 through a fastening iron ring 24, and forms a blocked cavity 30 with the water leakage pipe 3; the external end of the type I joint 2 is in threaded connection with a guide head 1; and the guide head 1 has a guide effect and is used to guide the test probe to smoothly slide in the drill hole 31.

The plugging device at the rear end 35 comprises two type III joints 7, a water leakage pipe 3 and a rubber bag 5; and the rubber bag 5 is fixed between the two type III joints 7 through a fastening iron ring 24.

A circular baffle 11 is installed outside the type III joints 7; the diameter of the circular baffle 11 is larger than the diameter of the rubber bag 5 to prevent the rubber bag 5 from falling; and the circular baffle 11 and the type III joints 7 are in threaded connection and are detachable to convenient replacement of the rubber bag 5.

The outside water source enters the blocked cavity 30 through the water leakage hole 25 in the plugging device at the front 34 and the plugging device at the rear end 35; the corresponding rubber bag 5 is inflated to form the water injection cavity 29 with the drill hole 31.

The left end and the right end of the pressure conversion assembly 47 are respectively in threaded connection with the connected pipe 28 and a type II joint 4; the high pressure water source in the connected pipe 28 is graded and converted by the first stage pressure converting device 6 and the second stage pressure converting device 37 successively into a low pressure water source and delivered into the water injection cavity 29.

A central through hole 32 and four peripheral through holes 33 are formed in the first stage pressure converting device 6; the four peripheral through holes 33 are symmetrically distributed around the central through hole 32; the central through hole 32 is a ladder port, where the left aperture is less than the right aperture; side drain holes 20 are formed in the side walls of the peripheral through holes 33.

A conversion body 10, an inner spring 9 and a regulating screw 8 are successively installed in the peripheral through holes 33; threads are arranged on the left inner walls of the peripheral through holes 33 and are matched with the regulating screw 8 so that the regulating screw 8 rotates and compresses the inner spring 9 within a certain range of the peripheral through holes 33 to control the opening pressure of the conversion body 10.

A hexagonal through hole 21 is formed in the side wall of the regulating screw 8 so that rotation of the regulating screw 8 is facilitated and feedback water pressure acts on the left end surface of the conversion body 10.

The conversion body 10 is a cylinder of unequal diameters, and the diameter of the left end surface of the conversion body 10 is larger than that of the right end surface; a sealed conical surface 26 is at the transition of the cylinder of unequal diameters, and coincides with the sealed conical surface 26 of the inner wall of the peripheral through holes 33; the sealed conical surface 26 has an angle of 30°.

An “L”-shaped limber of No. 1 23 is formed in the conversion body 10; an annular flume 22 is formed in a cylindrical external surface near the left end surface of the conversion body 10; the limber of No. 1 23 is communicated with the annular flume 22; and when the conversion body 10 moves to the left driven by the outside water source, the annular flume 22 is communicated with the side drain holes 20.

The second stage pressure converting device 37 comprises an external annular component 38, an internal annular component 39, an annular conversion body 40, an external spring 45 and a cross filiform ring 46; a thread is arranged on the right inner wall of the external annular component 38, is sheathed on the right outer wall of the first stage pressure converting device 6 and forms a central transitional cavity 48 with the first stage pressure converting device 6; and the side drain holes 20 and the hexagonal through hole 21 are communicated with the central transitional cavity 48.

The internal annular component 39 is in the shape of a cylindrical ring, and a thread is arranged on the inner wall of the internal annular component 39 and is wrapped around the outer wall of the connected pipe 28; four protruding parts 44 are arranged on the outer wall to limit the maximum leftward movement range of the annular conversion body 40; water collecting slots 42 and water diversion holes 43 are disposed in the pipe wall of the internal annular component 39; four water diversion holes 43 are disposed and are respectively vertically communicated with the water collecting slots 42 to diverse and drain water in the water collecting slots 42.

The annular conversion body 40 is positioned between the external annular component 38 and the internal annular component 39 and slides left and right along the surface of the internal annular component 39.

Four “L”-shaped limbers of No. 2 41 are correspondingly formed in the annular conversion body 40; when the annular conversion body 40 moves to the left, the limbers of No. 2 41 are communicated with the water collecting slots 42 to deliver the high pressure water source in the central transitional cavity 48 into the water collecting slots 42; at this moment, the left end surface of the annular conversion body 40 just comes into contact with the protruding part 44; and the diameter of the left end surface of the annular conversion body 40 is larger than that of the right end surface, and the sealed conical surface 26 is arranged in the middle connected position.

The external spring 45 is positioned between the annular conversion body 40 and the cross filiform ring 46, and has the same diameter as the left end surface of the annular conversion body 40.

The cross filiform ring 46 is in the shape of “cross”, and the middle position thereof is circular; a thread is arranged on the inner wall of the cross filiform ring 46 and is matched with the internal annular component 39; the cross filiform ring 46 rotates on the thread by means of an external tool to change the compression extent of the external spring 45 so as to control the opening pressure of the annular conversion body 40.

The working principle of the first stage pressure converting device is:

(1) when the conversion body 10 satisfies P_(mid)S_(left)+k_(inner)x≤P_(right)S_(right), the conversion body 10 moves to the left, and then the annular flume 22 is communicated with the side drain holes 20 to supply water into the central transitional cavity 48 to realize first stage pressure drop;

(2) when the conversion body 10 satisfies P_(mid)S_(left)+k_(inner)x≥P_(right)S_(right), the conversion body 10 moves to the right, and then the annular flume 22 is closed by the inner walls of the peripheral through holes 33 to stop supplying water into the central transitional cavity 48;

(3) if P_(right) is too large, in order to prevent extreme water pressure of P_(right) from damaging the inner wall of the drill hole in the water injection cavity 29 through the pressure conversion assembly 47, the conversion body 10 moves to the left under the action of the outside water source until the annular flume 22 moves to the left end of the side drain hole 20 and forms another closing role on the inner walls of the peripheral through holes 33,

wherein P_(mid) is the water source pressure of the central transitional cavity 48, which is generally 0.8 to 1 MPa; P_(light) is the pressure of the supplied water source in the connected pipe 28, which is generally about 1.5 MPa; S_(left) is the area of the left end surface of the conversion body; S_(right) is the area of the right end surface of the conversion body 10; k_(inner) is an elastic coefficient of the inner spring 9; and x is compression length.

The working principle of the second stage pressure converting device is:

(1) when the annular conversion body 40 satisfies P_(left)S_(left)+k_(outer)x≥P_(mid)S_(right), the annular conversion body 40 moves to the left and the limbers of No. 2 41 are communicated with the water collecting slots 42 to inject low water pressure into the water injection cavity 29 through the water diversion holes 43 to realize second stage pressure drop;

(2) when the annular conversion body 40 satisfies P_(left)S_(left)+k_(outer)x≥P_(mid)S_(right), the annular conversion body 40 moves to the right, and then the limbers of No. 2 41 are closed by the outer wall of the internal annular component 39 to stop supplying water into the water injection cavity 29;

wherein P_(left) is the observed water source pressure of the water injection cavity 29, which is generally about 0.2 to 0.5 MPa; P_(mid) is the pressure of the water source in the central transitional cavity 48, which is generally about 0.8 to 1 MPa; S_(left) is the flow area of the left end surface of the annular conversion body 40; S_(right) is the flow area of the right end surface of the annular conversion body 40; k_(outer) is an elastic coefficient of the external spring 45; and x is compression length.

The control operation platform 36 comprises a water release switch 15, a flow meter 16, a mechanical pressure gauge 17, a total control switch 18 and an electronic pressure gauge 19; the water release switch 15 is responsible for releasing pressure water in the test probe after pressurized pressure testing completed so that the rubber bag 5 is out of contact with the drill hole 31 to facilitate the drilling rig 14 in pushing the test probe; the total control switch 18 is responsible for interruption of the outside water source supply; the flow meter 16 is responsible for displaying the real-time water input from the external water source to the test probe; the mechanical pressure gauge 17 is compared with the reading of the electronic pressure gauge 19 for inspection; and if the mechanical pressure gauge 17 is roughly equal to the reading, then the pressure is effective.

A graded pressure drop type detection method of borehole cracks comprises the following steps:

(1) constructing drill holes: constructing three to five drill holes with different directions and inclined angles in the region of rock mass 27 to be detected through the drilling rig 14 in accordance with predesigned construction requirements; the drill holes 31 having a diameter of 89 mm and a length of about 70 m; and cleaning scraps in the drill holes 31;

(2) installing equipment: installing all components of the test probe; successively connecting the drilling rig 14, the drill pipe 12, the high pressure resistant hose 13 and the control operation platform 36; and then pushing the test probe to the initial positions of the drill holes 31 through the drilling rig 14;

(3) seal inspection: firstly, turning off a water release switch 15 of the control operation platform 36; turning on the total control switch 18 to provide detection water pressure for the test probe; conducting a plugging seal inspection on the rubber bag 5; conducting next operation if there is no obvious water leakage phenomenon; otherwise, returning to operation of step (2) to check the connection and installation among all components until qualified;

(4) detecting water leakage rate: conducting pressurized-water test after passing the seal inspection; allowing the test probe to be in the initial position; turning off the water release switch 15 and turning on the total control switch 18 to provide a high pressure water source for the test probe; allowing the water source to enter the blocked cavity 30 through the connected pipe 28 and the water leakage pipe 3; inflating the rubber bags 5 of the plugging device at the front 34 and the plugging device at the rear end 35 to form a water injection cavity 29 with the drill holes 31; adjusting the pressure of the outside water source to gradually rise to 1.5 MPa; converting the high pressure water source into a low pressure detection water source through the first stage pressure converting device 6 and the second stage pressure converting device 37 into the water injection cavity 29; and recording the steady reading Q_(i) of the flow meter and a detection length L_(i) after the reading of the flowmeter is steady;

(5) pressure relief propulsion: turning off the total control switch 18; turning on the water release switch 15 to release the pressure of the blocked cavity 30; turning off the water release switch 15 after the rubber bag 5 is out of contact with the drill holes 31; taking another drill pipe 12 to connect to the test probe; pushing the test probe to a next detection region through the drilling rig 14; and repeating the operation of step (4) until all lengths of the drill holes are detected;

(6) calculation and analysis: respectively drawing flow distribution maps in different drill holes according to the length of the drill holes and corresponding injected water leakage of drilling hole; analyzing fracture development and permeability characteristics at different positions within the length range of the drill holes; and further calculating failure range of the rock mass within different spatial ranges by combining the inclined angles of the drill holes in different directions with accumulated successive water leakage length L_(n) (n=1+2+ . . . +k).

The present invention has the following beneficial effects that:

(1) The present invention proposes a graded pressure drop type detection system of borehole cracks. Compared with the prior art, the detection system realizes plugging and leak detection integration of the test probe, reduces the number of the pipelines that work simultaneously in the drill holes as 1 pipeline, solves the multi pipe entanglement problem in the drill holes during propulsion and enhances the stability of the measurement process for the failure range of rock mass.

(2) The detection system solves the problem that the plugging process and the observation process operate under respective pressures through the same outside water source, avoids damaging the borehole cracks caused by ultrahigh pressure of the observation water source and enhances the accuracy of the measurement process of the failure range of rock mass.

(3) The detection system conducts gradient pressure conversion through the first stage pressure converting device and the second stage pressure converting device, enhances the stability of the working process of the pressure conversion assembly through the design of the sealed conical surface, adjusts compression length of the spring through screws (cross filiform rings), and controls the conversion body (annular conversion body) to have different opening pressures and conversion pressures so that the pressure adjusting range is more extensive and can adapt to different work needs.

(4) The design of the annular flume and the water collecting slots solves the problem that the limbers do not correspond to the water outlets, and ensures that the water in the limbers can flow through the annular flume to the converting device outlet no matter how the conversion body (annular conversion body) rotates.

DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic diagram of an overall structure and observation state of a graded pressure drop type detection system of borehole cracks in the present invention;

FIG. 2 is a schematic diagram of a pressure relief propulsion state of a graded pressure drop type detection system of borehole cracks in the present invention;

FIG. 3 is a structural schematic diagram of a test probe in a graded pressure drop type detection system of borehole cracks in the present invention;

FIG. 4 is a structural schematic diagram of a plugging device at the front in a graded pressure drop type detection system of borehole cracks in the present invention;

FIG. 5 is a structural schematic diagram of a plugging device at the rear end in a graded pressure drop type detection system of borehole cracks in the present invention;

FIG. 6 is a structural schematic diagram of a pressure conversion assembly in a graded pressure drop type detection system of borehole cracks in the present invention;

FIG. 7(a) is a structural main view of a first stage pressure converting device in a graded pressure drop type detection system of borehole cracks in the present invention;

FIG. 7(b) is a structural side view of a first stage pressure converting device in a graded pressure drop type detection system of borehole cracks in the present invention;

FIG. 8(a) is a schematic diagram of a stationary state of a first stage pressure converting device in a graded pressure drop type detection system of borehole cracks in the present invention;

FIG. 8(b) is a schematic diagram of a working state of a first stage pressure converting device in a graded pressure drop type detection system of borehole cracks in the present invention;

FIG. 9(a) is a structural main view of a conversion body in a graded pressure drop type detection system of borehole cracks in the present invention;

FIG. 9(b) is a structural back view of a conversion body in a graded pressure drop type detection system of borehole cracks in the present invention;

FIG. 9(c) is a structural side view of a conversion body in a graded pressure drop type detection system of borehole cracks in the present invention;

FIGS. 10(a) and 10(b) are structural schematic diagrams of a regulating screw in a graded pressure drop type detection system of borehole cracks in the present invention;

FIG. 11 is a structural schematic diagram of a second stage pressure converting device in a graded pressure drop type detection system of borehole cracks in the present invention;

FIG. 12 is a structural schematic diagram of an annular conversion body in a graded pressure drop type detection system of borehole cracks in the present invention;

FIG. 13(a) is a structural main view of an internal annular component in a graded pressure drop type detection system of borehole cracks in the present invention;

FIG. 13(b) is a structural side view of an internal annular component in a graded pressure drop type detection system of borehole cracks in the present invention; and

FIG. 14 is a structural schematic diagram of a cross filiform ring in a graded pressure drop type detection system of borehole cracks in the present invention.

In the figures: 1 guide head; 2 type I joint; 3 water leakage pipe; 4 type II joint; 5 rubber bag; 6 first stage pressure converting device; 7 type III joint; 8 regulating screw; 9 inner spring; 10 conversion body; 11 circular baffle; 12 drill hole; 13 high pressure resistant hose; 14 drilling rig; 15 water release switch; 16 flow meter; 17 mechanical pressure gauge; 18 total control switch; 19 electronic pressure gauge; 20 side drain hole; 21 hexagonal through hole; 22 annular flume; 23 limber of No. 1; 24 fastening iron ring; 25 water leakage hole; 26 sealed conical surface; 27 rock mass to be detected; 28 connected pipe; 29 water injection cavity; 30 blocked cavity; 31 drill hole; 32 central through hole; 33 peripheral through hole; 34 plugging device at the front; 35 plugging device at the rear end; 36 control operation platform; 37 second stage pressure converting device; 38 external annular component; 39 internal annular component; 40 annular conversion body; 41 limber of No. 2; 42 water collecting slot; 43 water diversion hole; 44 protruding part; 45 external spring; 46 cross filiform ring; 47 pressure conversion assembly; and 48 central transitional cavity.

DETAILED DESCRIPTION

Specific embodiments of the present invention are further described below in combination with accompanying drawings and the technical solution.

As shown in FIGS. 1-3, a graded pressure drop type detection system of borehole cracks mainly comprises a test probe, a drilling rig 14, a drill pipe 12 and a control operation platform 36.

The test probe mainly comprises a plugging device at the front 34, a plugging device at the rear end 35, and a pressure conversion assembly 47 connected to the rear end of the plugging device at the front 34. The pressure conversion assembly 47 is connected with the plugging device at the rear end 35 through a connected pipe 28 and mainly comprises a first stage pressure converting device 6 and a second stage pressure converting device 37. The second stage pressure converting device 37 is sheathed on the outer end of the first stage pressure converting device 6 and is in threaded connection with the first stage pressure converting device 6. The plugging device consists of a water leakage pipe 3, a series of joints and a rubber bag 5. The rubber bag 5 is wrapped around the outer end of the water leakage pipe 3, and forms a blocked cavity 30 with the water leakage pipe 3. Both ends of the rubber bag 5 are fixed by a fastening iron ring 24. A water leakage hole 25 is formed in the water leakage pipe 3. An outside water source enters the blocked cavity 30 through the water leakage hole 25. The rubber bag 5 is inflated to form a water injection cavity 29 with a drill hole 31.

The drilling rig 14 is connected with the test probe through the drill pipe 12 for extending and pushing the test probe to a designated region. The drill pipe 12 is a hollow pipe in which the outside high pressure water source can be delivered. The drill pipe 12 and the test probe are in threaded connection and are detachable.

The control operation platform 36 is connected with the drill pipe 12 through a high pressure resistant hose 13 and is responsible for providing the outside water source with designated pressure for the test probe and detecting parameters such as pressure and flow.

As shown in FIG. 4, the plugging device at the front 34 consists of a type I joint 2, a water leakage pipe 3, a type II joint 4 and a rubber bag 5. The type I joint 2, the type II joint 4 and the water leakage pipe 3 are in threaded connection. The rubber bag 5 is wrapped outside the water leakage pipe 3, is fixed outside the type I joint 2 and the type II joint 4 through a fastening iron ring 24, and forms a blocked cavity 30 with the water leakage pipe 3.

The external end of the type I joint 2 is in threaded connection with a guide head 1; and the guide head 1 has a guide effect and is used to guide the test probe to smoothly slide in the drill hole 31.

As shown in FIG. 5, the plugging device at the rear end 35 consists of two type III joints 7, a water leakage pipe 3 and a rubber bag 5; and the rubber bag 5 is fixed between the two type III joints 7 through a fastening iron ring 24.

A circular baffle 11 is installed outside the type III joints 7. The diameter of the circular baffle 11 is larger than that of the rubber bag 5 to prevent the rubber bag 5 from falling. The circular baffle 11 and the type III joints 7 are in threaded connection and are detachable to facilitate the replacement of the rubber bag 5.

The outside water source enters the blocked cavity 30 through the water leakage hole 25 in the plugging device at the front 34 and the plugging device at the rear end 35. The water injection cavity 29 is formed between the corresponding swelling rubber bags 5 and drill hole 31.

As shown in FIG. 6, the left end and the right end of the pressure conversion assembly 47 are respectively in threaded connection with the connected pipe 28 and a type II joint 4. The high pressure water source in the connected pipe 28 is graded and converted by the first stage pressure converting device 6 and the second stage pressure converting device 37 successively into a low pressure water source and delivered into the water injection cavity 29.

As shown in FIG. 7, a central through hole 32 and four peripheral through holes 33 are formed in the left end surface and the right end surface of the first stage pressure converting device 6. The four peripheral through holes 33 are symmetrically distributed around the central through hole 32.

The left aperture of the central through hole 32 is less than the right aperture. Side drain holes 20 are formed in the side walls of the peripheral through holes 33.

A conversion body 10, an inner spring 9 and a regulating screw 8 are successively installed in the peripheral through holes 33. Threads are arranged on the left inner walls of the peripheral through holes 33 and are matched with the regulating screw 8 so that the regulating screw 8 rotates and compresses the inner spring 9 within a certain range of the peripheral through holes 33 to control the opening pressure of the conversion body 10.

A hexagonal through hole 21 is formed in the side wall of the regulating screw 8 so that rotation of the regulating screw 8 is facilitated and feedback water pressure acts on the left end surface of the conversion body 10.

As shown in FIG. 9, the conversion body 10 is a cylinder of unequal diameters, and the diameter of the left end surface of the conversion body 10 is larger than that of the right end surface. A sealed conical surface 26 is at the transition of the cylinder of unequal diameters, and coincides with the sealed conical surface 26 of the inner wall of the peripheral through holes 33. The sealed conical surface 26 has an angle of 30°.

An “L”-shaped limber of No. 1 23 is formed in the conversion body 10. An annular flume 22 is formed in a cylindrical external surface near the left end surface of the conversion body 10. The limber of No. 1 23 is communicated with the annular flume 22. When the conversion body 10 moves to the left driven by the outside water source, the annular flume 22 is communicated with the side drain holes 20.

As shown in FIGS. 11-14, the second stage pressure converting device 37 comprises an external annular component 38, an internal annular component 39, an annular conversion body 40, an external spring 45 and a cross filiform ring 46; a thread is arranged on the right inner wall of the external annular component 38, is sheathed on the right outer wall of the first stage pressure converting device 6 and forms a central transitional cavity 48 with the first stage pressure converting device 6. The side drain holes 20 and the hexagonal through hole 21 are communicated with the central transitional cavity 48.

The internal annular component 39 is in the shape of a cylindrical ring, and a thread is arranged on the inner wall of the internal annular component 39 and is wrapped around the outer wall of the connected pipe 28; and four protruding parts 44 are arranged on the outer wall to limit the maximum leftward movement range of the annular conversion body 40. Water collecting slots 42 and water diversion holes 43 are disposed in the pipe wall of the internal annular component 39; and four water diversion holes 43 are disposed and are respectively vertically communicated with the water collecting slots 42 to diverse and drain water in the water collecting slots 42.

The annular conversion body 40 is positioned between the external annular component 38 and the internal annular component 39 and slides left and right along the surface of the internal annular component 39.

Four “L”-shaped limbers of No. 2 41 are correspondingly formed in the annular conversion body 40; when the annular conversion body 40 moves to the left, the limbers of No. 2 41 are communicated with the water collecting slots 42 to deliver the high pressure water source in the central transitional cavity 48 into the water collecting slots 42; and at this moment, the left end surface of the annular conversion body 40 just comes into contact with the protruding part 44. The diameter of the left end surface of the annular conversion body 40 is larger than that of the right end surface, and the sealed conical surface is arranged in the middle connected position.

The external spring 45 is positioned between the annular conversion body 40 and the cross filiform ring 46, and has the same diameter as the left end surface of the annular conversion body 40.

The cross filiform ring 46 is in the shape of “cross”, and the middle position thereof is circular; a thread is arranged on the inner wall of the cross filiform ring 46 and is matched with the internal annular component 39; the cross filiform ring 46 rotates on the thread by means of an external tool; and the compression extent of the external spring 45 is changed to control the opening pressure of the annular conversion body 40.

As shown in FIG. 8, the working principle of the first stage pressure converting device 6 is:

(1) when the conversion body 10 satisfies P_(mid)S_(left)+k_(inner)x≤P_(right)S_(right), the conversion body 10 moves to the left, and then the annular flume 22 is communicated with the side drain holes 20 to supply water into the central transitional cavity 48 to realize first stage pressure drop;

(2) when the conversion body 10 satisfies P_(mid)S_(left)+k_(inner)x≥P_(right)S_(right), the conversion body 10 moves to the right, and then the annular flume 22 is closed by the inner walls of the peripheral through holes 33 to stop supplying water into the central transitional cavity 48;

(3) if P_(right) is too large, in order to prevent extreme water pressure of P_(right) from damaging the inner wall of the drill hole 31 in the water injection cavity 29 through the pressure conversion assembly 47, the conversion body 10 moves to the left under the action of the outside water source until the annular flume 22 moves to the left end of the side drain hole 20 and forms another closing role on the inner walls of the peripheral through holes 33.

Wherein P_(mid) is the water source pressure of the central transitional cavity 48, which is generally 0.8 to 1 MPa. P_(right) is the pressure of the supplied water source in the connected pipe 28, which is generally about 1.5 MPa; S_(left) is the area of the left end surface of the conversion body 10; S_(right) is the area of the right end surface of the conversion body 10; k_(inner) is an elastic coefficient of the inner spring 9; and x is compression length.

The working principle of the second stage pressure converting device 37 is:

(1) when the annular conversion body 40 satisfies P_(left)S_(left)+k_(outer)x≤P_(mid)S_(right), the annular conversion body 40 moves to the left, and then the limbers of No. 2 41 are communicated with the water collecting slots 42 to inject low pressure water into the water injection cavity 29 through the water diversion holes 43 to realize second stage pressure drop;

(2) when the annular conversion body 40 satisfies P_(left)S_(left)+k_(outer)x≥P_(mid)S_(right), the annular conversion body 40 moves to the right, and then the limbers of No. 2 41 are closed by the outer wall of the internal annular component 39 to stop supplying water into the water injection cavity 29.

wherein P_(left) is the observed water source pressure of the water injection cavity 29, which is generally about 0.2 to 0.5 MPa; P_(mid) is the pressure of the water source in the central transitional cavity 48, which is generally about 0.8 to 1 MPa; S_(left) is the contact area between water and the left end surface of the annular conversion body 40; S_(right) is the contact area between water and the right end surface of the annular conversion body 40; k_(outer) is an elastic coefficient of the external spring 45; and x is compression length.

The control operation platform 36 mainly comprises a water release switch 15, a flow meter 16, a mechanical pressure gauge 17, a total control switch 18 and an electronic pressure gauge 19; and the water release switch 15 is responsible for releasing pressure water in the test probe after pressurized pressure testing completed so that the rubber bag 5 is out of contact with the drill hole 31 to facilitate the drilling rig 14 in pushing the test probe to next detection area. The total control switch 18 is responsible for interruption of the outside water source supply; the flow meter 16 is responsible for displaying the real-time water input from the external water source to the test probe; the mechanical pressure gauge 17 is compared with the reading of the electronic pressure gauge 19 for inspection; and if the mechanical pressure gauge 17 is roughly equal to the reading, then the pressure is effective.

A graded pressure drop type detection method of borehole cracks comprises the following steps:

(1) constructing drill holes 31: constructing three to five drill holes 31 with different directions and inclined angles in the region of rock mass 27 to be detected through the drilling rig 14 in accordance with predesigned construction requirements; the drill holes 31 having a diameter of 89 mm and a length of about 70 m; and cleaning scraps in the drill holes 31;

(2) installing equipment: installing all components of the test probe; successively connecting the drilling rig 14, the drill pipe 12, the high pressure resistant hose 13 and the control operation platform 36; and then pushing the test probe to the initial positions of the drill holes 31 through the drilling rig 14;

(3) seal inspection: firstly, turning off a water release switch 15 of the control operation platform 36; turning on the total control switch 18 to provide detection water pressure for the test probe; conducting a plugging seal inspection on the rubber bag 5; conducting next operation if there is no obvious water leakage phenomenon; otherwise, returning to operation of step (2) to inspect the connection and installation among all components; then conducting operation of step (3) until qualified;

(4) detecting water leakage rate: conducting pressurized-water test after passing the seal inspection; allowing the test probe to be in the initial position; turning off the water release switch 15 and turning on the total control switch 18 to provide a high pressure water source for the test probe; allowing the water source to enter the blocked cavity 30 through the connected pipe 28 and the water leakage pipe 3; inflating the rubber bags 5 of the plugging device at the front 34 and the plugging device at the rear end 35 to form a water injection cavity 29 with the drill holes 31; adjusting the pressure of the outside water source to gradually rise to 1.5 MPa; converting the high pressure water source into a low pressure detection water source through the first stage pressure converting device 6 and the second stage pressure converting device 37 into the water injection cavity 29; and recording the steady reading Q, of the flow meter 16 and a detection length L, after the reading of the flow meter 16 is steady;

(5) relief propulsion: turning off the total control switch 18; turning on the water release switch 15 to release the pressure of the blocked cavity 30; turning off the water release switch 15 after the rubber bag 5 is out of contact with the drill holes 31; taking another drill pipe 12 to connect to the test probe; pushing the test probe to a next detection region through the drilling rig 14; and repeating the operation of step (4) until all lengths of the drill holes 31 are detected;

6 calculation and analysis: respectively drawing flow distribution maps in different drill holes 31 according to the length of the drill holes 31 and corresponding injected water leakage of drilling hole; analyzing fracture development and permeability characteristics at different positions within the length range of the drill holes 31; and further calculating failure range of the rock mass within different spatial ranges by combining the inclined angles of the drill holes 31 in different directions with accumulated successive water leakage length L_(n) (n=1+2+ . . . +k).

The part not described in the present invention can be realized by adopting or referring to the prior art.

Although many terms such as the conversion body 10, the pressure conversion assembly 47 and the second stage pressure converting device 37 are used herein, it is also possible to use other terms. Simple replacements made to these terms by those skilled in the art under the enlightenment of the present invention shall be included within the protection scope of the present invention. 

1. A graded pressure drop type detection system of borehole cracks, comprising a test probe, a drilling rig, a drill pipe and a control operation platform, wherein the test probe comprises a plugging device and a pressure conversion assembly; the plugging device comprises a plugging device at the front and a plugging device at the rear end; the pressure conversion assembly is connected with the plugging device at the rear end through a connected pipe and comprises a first stage pressure converting device and a second stage pressure converting device; the second stage pressure converting device is sheathed on the outer end of the first stage pressure converting device and is in threaded connection with the first stage pressure converting device; the plugging device comprises a water leakage pipe, a joint and a rubber bag; the rubber bag is wrapped around the outer end of the water leakage pipe, and forms a blocked cavity with the water leakage pipe; both ends of the rubber bag are fixed by a fastening iron ring; a water leakage hole is formed in the water leakage pipe; an outside water source enters the blocked cavity through the water leakage hole in the water leakage pipe; a water injection cavity is formed between the swelling rubber bags and drill hole; the drilling rig is connected with the test probe through the drill pipe for extending and pushing the test probe to a designated region; the drill pipe is a hollow pipe in which the outside high pressure water source can be delivered; the drill pipe and the test probe are in threaded connection and are detachable; the control operation platform is connected with the drill pipe through a high pressure resistant hose and is responsible for providing the outside water source with designated pressure for the test probe and displaying pressure and flow values; the outside water source enters the blocked cavity through the water leakage hole in the plugging device at the front and the plugging device at the rear end; the water injection cavity is formed between the corresponding swelling rubber bags and drill hole; the left end and the right end of the pressure conversion assembly are respectively in threaded connection with the connected pipe and a type II joint; the high pressure water source in the connected pipe is graded and converted by the first stage pressure converting device and the second stage pressure converting device successively into a low pressure water source and delivered into the water injection cavity; a central through hole and four peripheral through holes are formed in the first stage pressure converting device; the four peripheral through holes are symmetrically distributed around the central through hole; the central through hole is a ladder port, where the left aperture is less than the right aperture; side drain holes are formed in the side walls of the peripheral through holes; a conversion body, an inner spring and a regulating screw are successively installed in the peripheral through holes; threads are arranged on the left inner walls of the peripheral through holes and are matched with the regulating screw so that the regulating screw rotates and compresses the inner spring within a certain range of the peripheral through holes to control the opening pressure of the conversion body; a hexagonal through hole is formed in the side wall of the regulating screw so that rotation of the regulating screw is facilitated and feedback water pressure acts on the left end surface of the conversion body; the conversion body is a cylinder of unequal diameters, and the diameter of the left end surface of the conversion body is larger than the diameter of the right end surface; a sealed conical surface is at the transition of the cylinder of unequal diameters, and coincides with the sealed conical surface of the inner wall of the peripheral through holes; the sealed conical surface has an angle of 30°; an “L ”-shaped limber of No. 1 is formed in the conversion body; an annular flume is formed in a cylindrical external surface near the left end surface of the conversion body; the limber of No. 1 is communicated with the annular flume; when the conversion body moves to the left driven by the outside water source, the annular flume is communicated with the side drain holes; the second stage pressure converting device comprises an external annular component, an internal annular component, an annular conversion body, an external spring and a cross filiform ring; a thread is arranged on the right inner wall of the external annular component, is sheathed on the right outer wall of the first stage pressure converting device, and a central transitional cavity is formed with the first stage pressure converting device; the side drain holes and the hexagonal through hole are communicated with the central transitional cavity; the internal annular component is in the shape of a cylindrical ring, and a thread is arranged on the inner wall of the internal annular component and is wrapped around the outer wall of the connected pipe; four protruding parts are arranged on the outer wall of the internal annular component to limit the maximum leftward movement range of the annular conversion body; water collecting slots and water diversion holes are disposed in the pipe wall of the internal annular component; four water diversion holes are disposed and are respectively vertically communicated with the water collecting slots to diverse and drain water in the water collecting slots; the annular conversion body is positioned between the external annular component and the internal annular component and slides left and right along the surface of the internal annular component; four “L”-shaped limbers of No. 2 are correspondingly formed in the annular conversion body; when the annular conversion body moves to the left, the limbers of No. 2 are communicated with the water collecting slots to deliver the high pressure water source in the central transitional cavity into the water collecting slots; at this moment, the left end surface of the annular conversion body just comes into contact with the protruding part; the diameter of the left end surface of the annular conversion body is larger than that of the right end surface, and the sealed conical surface is arranged in the middle connected position; the external spring is positioned between the annular conversion body and the cross filiform ring, and has the same diameter as the left end surface of the annular conversion body; the cross filiform ring is in the shape of “cross”, and the middle position thereof is circular; a thread is arranged on the inner wall of the cross filiform ring and is matched with the internal annular component; the cross filiform ring rotates on the thread by means of an external tool to change the compression extent of the external spring so as to control the opening pressure of the annular conversion body; the working principle of the first stage pressure converting device is: (1) when the conversion body satisfies P_(mid)S_(left)+k_(inner)≤P_(right)S_(right), the conversion body moves to the left, and then the annular flume is communicated with the side drain holes to supply water into the central transitional cavity to realize first stage pressure drop; (2) when the conversion body satisfies P_(mid)S_(left)+k_(inner)≥P_(right)S_(right), the conversion body moves to the right, and then the annular flume is closed by the inner walls of the peripheral through holes to stop supplying water into the central transitional cavity; (3) if P_(right) is too large, in order to prevent extreme water pressure of P_(right) from damaging the inner wall of the drill hole in the water injection cavity through the pressure conversion assembly, the conversion body moves to the left under the action of the outside water source until the annular flume moves to the left end of the side drain hole and forms another closing role on the inner walls of the peripheral through holes; wherein P_(mid) is the water source pressure of the central transitional cavity, ranging from 0.8 to 1 MPa. P_(right) is the pressure of the supplied water source in the connected pipe, which is 1.5 MPa; S_(left) is the area of the left end surface of the conversion body; S_(right) is the area of the right end surface of the conversion body; k_(inner) is an elastic coefficient of the inner spring; and x is compression length; the working principle of the second stage pressure converting device is: (1) the annular conversion body satisfies P_(left)S_(left)+k_(outer)≤P_(mid)S_(right), the annular conversion body moves to the left, and then the limbers of No. 2 are communicated with the water collecting slots to inject low pressure water into the water injection cavity through the water diversion holes to realize second stage pressure drop; (2) when the annular conversion body satisfies P_(left)S_(left)+k_(outer)≥P_(mid)S_(right), the annular conversion body moves to the right, and then the limbers of No. 2 are closed by the outer wall of the internal annular component to stop supplying water into the water injection cavity; wherein P_(left) is the observed water source pressure of the water injection cavity, ranging from 0.2 to 0.5 MPa; P_(mid) is the pressure of the water source in the central transitional cavity, ranging from 0.8 to 1 MPa; S_(left) is the contact area between water and the left end surface of the annular conversion body; S_(right) is the contact area between water and the right end surface of the annular conversion body; k_(outer) is an elastic coefficient of the external spring; and x is compression length; the control operation platform comprises a water release switch, a flow meter, a mechanical pressure gauge, a total control switch and an electronic pressure gauge the water release switch is responsible for releasing pressure water in the test probe after pressurized pressure testing completed so that the rubber bag is out of contact with the drill hole to facilitate the drilling rig in pushing the test probe, the total control switch is responsible for interruption of the outside water source supply; the flow meter is responsible for displaying the real-time water input from the external water source to the test probe; the mechanical pressure gauge is compared with the reading of the electronic pressure gauge for inspection; if the mechanical pressure gauge is roughly equal to the reading, then the pressure is effective.
 2. The graded pressure drop type detection system of borehole cracks according to claim 1, wherein the plugging device at the front consists of a type I joint, a water leakage pipe, a type II joint and a rubber bag; the type I joint, the type II joint and the water leakage pipe are in threaded connection; the rubber bag is wrapped outside the water leakage pipe, is fixed outside the type I joint and the type II joint through a fastening iron ring, and forms a blocked cavity with the water leakage pipe; the external end of the type I joint is in threaded connection with a guide head; and the guide head has a guide effect and is used to guide the test probe to smoothly slide in the drill hole.
 3. The graded pressure drop type detection system of borehole cracks according to claim 1, wherein the plugging device at the rear end comprises two type III joints, a water leakage pipe and a rubber bag; and the rubber bag is fixed between the two type III joints through a fastening iron ring.
 4. The graded pressure drop type detection system of borehole cracks according to claim 3, wherein a circular baffle is installed outside the type III joints the diameter of the circular baffle is larger than that of the rubber bag to prevent the rubber bag from falling; and the circular baffle and the type III joints are in threaded connection and are detachable to convenient replacement of the rubber bag.
 5. A graded pressure drop type detection method of borehole cracks, comprising the following steps: (1) constructing drill holes: constructing three to five drill holes with different directions and inclined angles in the region of rock mass to be detected through the drilling rig in accordance with predesigned construction requirements; the drill holes having a diameter of 89 mm and a length of about 70 m; and cleaning scraps in the drill holes; (2) installing equipment: installing all components of the test probe; successively connecting the drilling rig, the drill pipe, the high pressure resistant hose and the control operation platform; and then pushing the test probe to the initial positions of the drill holes through the drilling rig; (3) seal inspection: firstly, turning off a water release switch of the control operation platform; turning on the total control switch to provide detection water pressure for the test probe; conducting a plugging seal inspection on the rubber bag; conducting next operation if there is no obvious water leakage phenomenon, otherwise, returning to operation of step to inspect the connection and installation among all components until qualified, (4) detecting water leakage rate: conducting pressurized-water test after passing the seal inspection; allowing the test probe to be in the initial position; turning off the water release switch and turning on the total control switch to provide a high pressure water source for the test probe, allowing the water source to enter the blocked cavity through the connected pipe and the water leakage pipe; inflating the rubber bags of the plugging device at the front and the plugging device at the rear end to form a water injection cavity with the drill holes; adjusting the pressure of the outside water source to gradually rise to 1.5 MPa; converting the high pressure water source into a low pressure detection water source through the first stage pressure converting device and the second stage pressure converting device into the water injection cavity; and recording the steady reading Q_(i) of the flow meter and a detection length L_(i) after the reading of the flow meter is steady; (5) pressure relief propulsion: turning off the total control switch; turning on the water release switch to release the pressure of the blocked cavity; turning off the water release switch after the rubber bag is out of contact with the drill holes; taking another drill pipe to connect to the test probe, pushing the test probe to a next detection region through the drilling rig; and repeating the operation of step until all lengths of the drill holes is detected; (6) calculation and analysis: respectively drawing flow distribution maps in different drill holes according to the length of the drill holes and corresponding injected water leakage of drilling hole; analyzing fracture development and permeability characteristics at different positions within the length range of the drill holes; and further calculating failure range of the rock mass within different spatial ranges by combining the inclined angles of the drill holes in different directions with accumulated successive water leakage length L_(n) (n=1+2+ . . . +k). 